X-ray Diffraction (XRD)

BY

SIWAPHIWE PETENI

Electromagnetic spectrum

Wilhelm Conrad Rontgen discovered X-ray in 1895

Nobel prize in physics in 1901

X-ray are high frequency electromagnetic radiation with energy

intermediate between the far UV and gamma region

English physicists Sir William.Hanry. Bragg and his son Sir William.Lawrence. Bragg

In 1913 developed a relationship to explain why the cleavage faces of crystals appear to reflect X-ray beams at certain angles of incidence (theta, q)

X-ray diffraction

XRD is a non-destructive technique

Is rapidly used for phase identification of a crystalline material and can provide information on unit cell dimensions

Single crystal

Polycrystalline Amorphous

Typical XRD machine

X-ray cube Detector Sample holder

Principle X-ray tube

Detector

Collimators

Matched filters

Crystal

Constructive interference only occurs for certain θ’s correlating to a (hkl) plane, specifically when the path difference is equal to n wavelengths.

Incident Diffracted beam

Application

To identify crystalline phases

Lattice parameters strain, grain size

Measure thickness of thin films

To determine atomic arrangement

Strengths

Easy to handle

Can be used to determine unknown mineral

Minimal sample preparation is required

XRD units are widely available

Data interpretation is relatively straight forward

Limitations

Not sensitive

Requires tenths of a gram of material which must be ground into a powder

For mixed materials, detection limit is ~ 2% of sample

Peak overlay may occur and worsens for high angle 'reflections

XRD

40 80-60

0

60

120

Intensi

ty/a.u

2theta/degree

2 theta/degrees

Inte

nsity

,au

(111)

(200) (220)

Acknowledgements Prof Nyokong

S22 lab mates

Tha